Add support for fetching remove imags for PDF

Author: dragonstyle

src/resources/filters/quarto-post/svg.lua …urces/filters/quarto-post/pdf-images.luasrc/resources/filters/quarto-post/svg.lua renamed to src/resources/filters/quarto-post/pdf-images.lua src/resources/filters/quarto-post/svg.lua renamed to src/resources/filters/quarto-post/pdf-images.lua

@@ -13,12 +13,17 @@ local function convert_svg(path)
   end
 end
 
-function svg() 
+-- A cache of image urls that we've resolved into the mediabag
+-- keyed by {url: mediabagpath}
+local resolvedUrls = {}
+
+function pdfImages() 
   return {
     -- convert SVG images to PDF when rendering PDFS
     Image = function(image)
       if quarto.doc.is_format("pdf") then
         if _quarto.file.exists(image.src) then
+          -- If the src is pointing to a local file that is an svg, process it
           local ext = select(2, pandoc.path.split_extension(image.src))
           if ext == '.svg' then
             local converted = convert_svg(image.src)
@@ -28,7 +33,8 @@ function svg()
             end
           end
         else
-          -- take a look in the media bag
+          -- See if the path points to an SVG in the media bag
+          -- (been generated by a filter, for example)
           local mt, contents = pandoc.mediabag.lookup(image.src)
           if mt == 'image/svg+xml' then
             local result = pandoc.system.with_temporary_directory('svg-convert', function (tmpdir) 
@@ -58,6 +64,32 @@ function svg()
               return nil
             end)
             return result
+          elseif mt == nil then
+            -- This file doesn't exist and isn't in the media bag
+            -- see if it need to be fetched
+            if resolvedUrls[image.src] then
+              image.src = resolvedUrls[image.src]
+              return image
+            else 
+              local relativePath = image.src:match('http[s]://[%w%.%:]+/(.+)')
+              if relativePath then
+                local imgMt, imgContents = pandoc.mediabag.fetch(image.src)
+                local filename = pandoc.path.filename(relativePath)
+                if imgMt ~= nil then
+                  local existingMt = pandoc.mediabag.lookup(filename)
+                  local counter = 1
+                  while (existingMt) do
+                    local stem, ext = pandoc.path.split_extension(filename)
+                    filename = stem .. counter .. ext
+                    existingMt = pandoc.mediabag.lookup(filename)
+                  end
+                  resolvedUrls[image.src] = filename
+                  pandoc.mediabag.insert(filename, imgMt, imgContents)
+                  image.src = filename
+                  return image
+                end
+              end
+            end
           end
         end
       end

src/resources/filters/quarto-post/quarto-post.lua

@@ -23,7 +23,7 @@ import("tikz.lua")
 import("meta.lua")
 import("delink.lua")
 import("book.lua")
-import("svg.lua")
+import("pdf-images.lua")
 import("../common/lunacolors.lua")
 import("../common/log.lua")
 import("../common/base64.lua")
@@ -48,7 +48,7 @@ return {
     tikz(),
     delink(),
     figCleanup(),
-    svg()
+    pdfImages()
   }),
   ojs(),
   quartoPostMetaInject(),